This invention relates to cooling apparatus for a locomotive engine and a method for operating the cooling apparatus.
Most modem railway road locomotives are of a diesel-electric type in which a diesel engine drives electrical generating apparatus to power electric motors that drive the locomotive wheels. The engine is typically turbocharged and includes one or more aftercoolers to remove some of the heat of compression from the turbocharged air before it enters the engine. An engine cooling system circulates liquid coolant through an engine coolant loop to remove heat from the engine and through an aftercooler coolant loop to remove heat from the aftercooler.
U.S. Pat. No. 5,598,705, Turbocharged Engine Cooling Apparatus, issued Feb. 4, 1997 describes cooling apparatus for a diesel-electric locomotive which employs separate engine and aftercooler coolant loops, each with its own radiator and pump apparatus and separate coolant conduits but sharing a single coolant tank. The loops are also connected by a linking conduit connecting the outlet of the aftercooler radiator with the inlet of the engine coolant pump. A valve in the linking conduit can be closed to prevent linking coolant flow; and the system is designed to operate in that manner under normal conditions, with the engine radiator and conduits sized to provide sufficient cooling for the engine and optional oil cooler in normal warmed up operation while the aftercooler radiator provides cooling of the turbocharged air for maximum fuel economy and low emissions. The engine radiator is not designed to provide sufficient engine cooling for extremely hot running conditions, but the valve can be opened as necessary in such conditions to admit low temperature coolant from the aftercooler coolant loop to the engine cooling loop for extra engine cooling, with return flow through the coolant tank.
U.S. Pat. No. 6,006,731, issued Dec. 28, 1999, discloses a modification in which the valved (third) linking conduit is moved to connect the engine coolant loop between the engine and engine radiator with the aftercooler coolant loop between the aftercooler and the aftercooler radiator. An additional (first) linking conduit bypassing the linking valve is also provided to pass some of the engine coolant through the aftercooler radiator at all times, leaving the linking valve to control additional linking flow as needed. Return flow from the aftercooler coolant loop to the engine coolant loop passes through a second linking conduit located as before between the radiators and their respective pumps and may pass through the coolant tank.
The radiators are arranged in two banks disposed in V orientation in a cooling chamber of the locomotive body. The banks are of equal cooling capacity, one bank connected in the main engine cooling loop and the other bank connected in the aftercooler cooling loop, but also providing a portion of the engine cooling. Electrically driven cooling fans are provided for drawing ambient cooling air through both radiator banks. The fan speeds and the operation of a linking valve controller may be controlled by a computer to maintain fuel economy and emissions at desired levels.
The present invention provides a further modified locomotive engine cooling system designed to further reduce engine emissions and improve engine efficiency. The concept is drawn from a recognition that aftercooling is a method that is capable of reducing both engine emissions and engine fuel consumption at the same time. A study of how aftercooling could be increased or optimized showed that the prior aftercooler systems previously discussed have the capability to increase aftercooling capacity by optimizing the flow rate of the aftercooler coolant loop. As applied to these prior systems, it was determined that by reducing and optimizing the aftercooler loop coolant flow rate, the amount of heat transfer from the engine inlet air to the radiator cooling air could be increased. Thus, a significant increase in aftercooling could be obtained by reducing the coolant temperature at the inlet of the aftercooler and this could be accomplished by reducing the rate of flow of coolant in the aftercooler loop. This improvement and how it may be applied in practice are fundamental features of the cooling system and method of the present invention.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.